Why comet tails point away from sun

By: David Dickinson August 25, By: Lauren Sgro August 5, By: Maria Temming July 15, By: Jeff Hecht June 22, By: Lauren Sgro June 17, Constant Contact Use. A comet has a distinct center called a nucleus. Most astronomers think the nucleus is made of frozen water and gases mixed with dust and rocky material. Comet nuclei are described as dirty snowballs.

A hazy cloud called a coma surrounds the nucleus. The coma and the nucleus together form the comet's head. Comet West The parts of a comet Comets follow a regular orbit around the Sun. If the comet nucleus is pulled into an orbit which carries it close to the Sun, the solar heat will cause the outer layers of the icy nucleus to evaporate. During this process, dust and gases which form the coma around the nucleus are released.

As the comet gets closer to the Sun, the coma grows. These gases form the plasma tail. This picture of the comet Hale-Bopp was photographed over Boulder, Colorado during its appearance in Dust-size particles that escape from the comet experience a much weaker push from the Sun caused by the pressure of sunlight itself called radiation pressure , rather than by the charged particles of the solar wind.

While the dust tail also points generally away from the Sun, it has a slight curve back in the direction the comet came from. What's so special about these random balls of ice and dust?

Comets are made up of the most primitive material in the solar system. That is, their composition has changed very little in the last 4 billion years. A better understanding of their composition and origin gives scientists clues about the origin of our solar system and helps to test the theories we have built about out evolution. The Stardust spacecraft was launched on February 7, , and returned safely to Earth on January 15, It was the first mission dedicated entirely to the exploration of a comet, and the first mission to bring back material from outside the orbit of the Moon.

The mission included a flyby of the asteroid Annefrank where the spacecraft took pictures and measurements of the mountain-sized rock. As comets move close to the Sun, they develop tails of dust and ionized gas. Comets have two main tails, a dust tail and a plasma tail. The dust tail appears whitish-yellow because it is made up of tiny particles — about the size of particles of smoke — that reflect sunlight. Dust tails are typically between 1 and 10 million kilometers about , to 6 million miles long.

The plasma tail is often blue because it contains carbon monoxide ions. Solar ultraviolet light breaks down the gas molecules, causing them to glow. Plasma tails can stretch tens of millions of kilometers into space. Rarely, they are as long as million kilometers almost million miles. A third tail of sodium has been observed on Comet Hale-Bopp. Comet Hale Bopp, taken by Joe Orman, showing the long, straight, blue plasma tail and the broader, shorter, whitish dust tail. Orman motorola. Comets are enveloped in a broad, thin sparse hydrogen cloud that can extend for millions of kilometers.

This envelope cannot be seen from Earth because its light is absorbed by our atmosphere, but it has been detected by spacecraft. How are comets named? Comets are named after the person who first reports their discovery.

For example, Comet Halley is named for Edmund Halley, who determined that comets observed in , , and had essentially the same orbits and thus were a single comet. Based on his calculations, he correctly predicted the comet's return in , but unfortunately, he did not live to see Comet Halley. Sometimes more than one person reports a new comet at the same time. Comet Halley, viewed in the spring of Detachment Event - Halley's Comet.

How big are comets? A comet's nucleus is typically 1 to 10 kilometers 0.